This invention relates to an apparatus for detecting the distribution of an electric surface potential and generating an electric signal representative of the detected potential distribution.
In some image pickup systems, a photoelectric transducing section enables a charge storage member to be charged in accordance with an optical image of an object. The distribution of an electric surface potential of the charge storage member represents the optical image. For example, a surface potential sensor of an electrostatic induction type is usable in detecting the distribution of such an electric surface potential and generating a corresponding electric signal.
Since the sensing section of such a surface potential sensor has a very high impedance, an impedance converter is generally connected to an output terminal of the sensing section. In the case where the impedance converter uses a field effect transistor, a leakage current from the drain to the gate of the transistor tends to cause an adverse effect such as an inaccuracy in the sensor output signal.